Laser sustained plasmas (LSPs) can be employed as illumination sources and are typically superior in brightness to electrical discharge lamps, carbon dioxide (CO2), direct diode, or fiber lasers are often used as pump sources for these plasmas.
Very high operating power of the lasers is required to pump LSP. Typically, high-power regime of operation starts at approximately a few hundred Watt of continuous wave (CW) pump power. Some solutions employ CW lasers which operate in the IR spectral range. In the high-power regime, the plasmas start to increase in size with power, growing in the direction of the pump laser. Plasma growth limits the temperature that can be achieved in the plasma center and thus limits the maximum spectral radiance that can be achieved. The size of the plasma is correlated to plasma absorption at the temperatures near the plasma sustainability threshold. Typically, absorption of the plasmas at these temperatures (e.g., about 10,000K) is stronger in the infrared (IR) spectral range than in the visible (VIS) spectral range. Thus, when pumped by IR illumination, LSPs tend to have larger size compared to LSPs pumped by shorter wavelength illumination. Few lasers are available in high-power, multi-kW regime in the VIS spectral range when operating in CW. This limits the application of VIS lasers for pumping LSP.